Wire Gauge/Breaker Size for 3-Ton A/C Unit

[Tom in Seattle]

My 3-ton A/C unit was installed by the vendor using the existing old hot tub wiring and breaker, which was 8 AWG THHN/THWN in conduit on the outside of the garage, connected to an existing 40A breaker.

I downloaded the specs for the A/C unit and it lists the minimum ampacity as 21.5A with a max size 35A breaker.

Thus, the 40A is really too large.

When I replace the SE panel I want to replace the wiring in conduit and run it through the wall, which will be covered.

Would 10/2 Romex on a 30A breaker be sufficient? I believe there are 35A breakers for my QO panel, but they are not stocked in the big box stores so are kind of an odd-ball size.

Thanks.

 

[pattenp]

#10 on 30A breaker is okay for your heat pump. I have two 2-1/2 Ton heat pump units and they are both wired with #10 on 30A breakers.

 

[Tom in Seattle]

Thanks for the confirmation. That's what I thought. I'll go with 10/2 and 30A. I'm sure the installation folks just used the existing wiring and breaker because they were already there, and I'm sure they never read the specs to see what the actual requirements were. They did update the service disconnect box to include a 20A receptacle, which they said was required for maintenance purposes.

 

[Norcal]

If it's not Romex (NM) cable, 12 AWG on a 35A breaker is code compliant....

 

[Aceman]

You are also required to have a receptacle within 25' of an HVAC unit. If you already have one, great. If not, you need to add one. I personally like to use the combination AC disconnect/GFCI receptacle enclosure, kills two birds with one stone. The type I use is a Siemens.

 

[Tom in Seattle]

They did update the service disconnect box to include a 20A receptacle, which they said was required for maintenance purposes.

Thanks for the info on the Siemens disconnect box Aceman. I do have a combination box as indicated above, but may decide to replace it.

Now... if I want to run the wires in the wall instead of in PVC conduit outside along the garage wall, what type of connector or fitting should I use to penetrate the wall? I haven't pulled the box off yet but I assume it has rear knockouts in addition to the ones that were used in the bottom. Routing the wiring from the rear would make a cleaner installation.

Could I use one of those 90 deg PVC boxes with the removable cover, but put it on the interior wall and run a short piece of conduit through the wall?

 

[Aceman]

Are you using Romex or conduit to feed this?

Romex, just use plastic Romex connectors through the back of it.

Pvc, use an LB or 4 square box on the inside with a short ****** through the wall.

 

[Gregishome]

You are also required to have a receptacle within 25' of an HVAC unit. If you already have one, great. If not, you need to add one. I personally like to use the combination AC disconnect/GFCI receptacle enclosure, kills two birds with one stone. The type I use is a Siemens.

Question on this post. Will the OP be running a seperate service line for the GFI ?

 

[Norcal]

Question on this post. Will the OP be running a seperate service line for the GFI ?

It should be for a # of reasons & it's not allowed to connect them on the load side of the disco...

 

[Tom in Seattle]

Question on this post. Will the OP be running a seperate service line for the GFI ?

Yes, as Norcal points out it is illegal to tap power off the AC circuit. I'll be running 10/2 Romex for the AC ; a separate run of 12/2 will provide power to the GFCI receptacle. The old original hot tub disconnect only included wires for the hot tub. When the AC was installed the installer was able to pull some #12 THHN through the original conduit and that currently provides power to the GFCI in the disconnect box.

Funny thing, I tried to find out who manufactures my current disconnect box but nowhere on any label is that information supplied. It seems that the Siemens, GE and maybe others are all made by the same supplier since they all look identical. I found a combination disconnect box made by Tork that looks nice. The model I'm looking at uses a switch instead of a pull-type disconnect. It also has a hinged cover instead of the swing-up type I have now, which I think would make it easier to work on.

 

[Gregishome]

Yes, as Norcal points out it is illegal to tap power off the AC circuit. I'll be running 10/2 Romex for the AC ; a separate run of 12/2 will provide power to the GFCI receptacle. The old original hot tub disconnect only included wires for the hot tub. When the AC was installed the installer was able to pull some #12 THHN through the original conduit and that currently provides power to the GFCI in the disconnect box.

Funny thing, I tried to find out who manufactures my current disconnect box but nowhere on any label is that information supplied. It seems that the Siemens, GE and maybe others are all made by the same supplier since they all look identical. I found a combination disconnect box made by Tork that looks nice. The model I'm looking at uses a switch instead of a pull-type disconnect. It also has a hinged cover instead of the swing-up type I have now, which I think would make it easier to work on.

I know the GFCI tap from a HVAC disconnect is illegal, I started doing electrical work out of school in 1970, and have been a licensed contractor since for residential, commercial work. Age has got me now to where I just do service /maintenance lightly..

I felt the need to bring up the issue, as the only source of power mentioned by the OP was the 220V - 10-2 WG romex installation. I am not on the jobsite so sometimes I ask questions, rather than see someone make a mistake. Good luck on your project.

 

[Tom in Seattle]

I am not on the jobsite so sometimes I ask questions, rather than see someone make a mistake. Good luck on your project.

Asking questions is always a good thing. It's how we learn, and I still have a lot to learn